Bortezomib inhibits chikungunya virus replication by interfering with viral protein synthesis.

Parveen Kaur,Laura Sandra Lello,Sujit Krishna Dutta,Age Utt,Justin Jang Hann Chu,Andres Merits,Abdallah M Samy

doi:10.1371/journal.pntd.0008336

Abstract

Chikungunya virus (CHIKV) is an alphavirus that causes a febrile illness accompanied by myalgia and arthralgia. Despite having re-emerged as a significant public health threat, there are no approved therapeutics or prophylactics for CHIKV infection. In this study, we explored the anti-CHIKV effects of proteasome inhibitors and their potential mechanism of antiviral action. A panel of proteasome inhibitors with different functional groups reduced CHIKV infectious titers in a dose-dependent manner. Bortezomib, which has been FDA-approved for multiple myeloma and mantle cell lymphoma, was further investigated in downstream studies. The inhibitory activities of bortezomib were confirmed using different cellular models and CHIKV strains. Time-of-addition and time-of-removal studies suggested that bortezomib inhibited CHIKV at an early, post-entry stage of replication. In western blot analysis, bortezomib treatment resulted in a prominent decrease in structural protein levels as early as 6 hpi. Contrastingly, nsP4 levels showed strong elevations across all time-points. NsP2 and nsP3 levels showed a fluctuating trend, with some elevations between 12 to 20 hpi. Finally, qRT-PCR data revealed increased levels of both positive- and negative-sense CHIKV RNA at late stages of infection. It is likely that the reductions in structural protein levels is a major factor in the observed reductions in virus titer, with the alterations in non-structural protein ratios potentially being a contributing factor. Proteasome inhibitors like bortezomib likely disrupt CHIKV replication through a variety of complex mechanisms and may display a potential for use as therapeutics against CHIKV infection. They also represent valuable tools for studies of CHIKV molecular biology and virus-host interactions.

Highlights

Chikungunya virus (CHIKV) is a mosquito-borne virus that has re-emerged as a major public health threat in the last decade [1, 2]
Chikungunya virus (CHIKV) is a mosquito-transmitted virus that causes an illness with debilitating muscle and joint pain
We found that bortezomib resulted in a major decrease in levels of CHIKV structural proteins, which are involved in formation of progeny virus particles

Summary

Author summary

Chikungunya virus (CHIKV) is a mosquito-transmitted virus that causes an illness with debilitating muscle and joint pain. There are no approved antivirals or vaccines against CHIKV infection. We explored the inhibitory effects of proteasome inhibitors against CHIKV. A panel of proteasome inhibitors was found to reduce CHIKV titres in CHIKV-infected cells. An FDA-approved drug, for further investigation into its antiviral mechanism. We found that bortezomib resulted in a major decrease in levels of CHIKV structural proteins, which are involved in formation of progeny virus particles. We propose that proteasome inhibitors like bortezomib are likely to inhibit CHIKV through various mechanisms that lead to a decrease in structural proteins and infectious viral progeny. This study suggests that proteasome inhibitors display a potential for further development as antivirals against CHIKV infection and may be useful tools to study CHIKV molecular biology and virus-host interactions

Introduction

Results

Materials and methods